Obesity is a major public health concern because of its increasing prevalence and associated health risks. Moreover, obesity may affect a person's quality of life through limited mobility and decreased physical endurance as well as through social, academic and job discrimination.
Obesity and overweight are generally defined by body mass index (BMI), which is correlated with total body fat and serves as a measure of the risk of certain diseases. BMI is calculated by weight in kilograms divided by height in meters squared (kg/m2). Overweight is typically defined as a BMI of 25-29.9 kg/m2, and obesity is typically defined as a BMI of 30 kg/m2 or higher. See, e.g., National Heart, Lung, and Blood Institute, Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults, The Evidence Report, Washington, D.C.: U.S. Department of Health and Human Services, NIH publication no. 98-4083 (1998).
Recent studies have found that obesity and its associated health risks are not limited to adults, but also affect children and adolescents to a startling degree. According to the Center for Disease Control, the percentage of children and adolescents who are defined as overweight has more than doubled since the early 1970s, and about 15 percent of children and adolescents are now overweight. Risk factors for heart disease, such as high cholesterol and high blood pressure, occur with increased frequency in overweight children and adolescents compared with normal-weight subjects of similar age. Also, type 2 diabetes, previously considered an adult disease, has increased dramatically in children and adolescents. Overweight conditions and obesity are closely linked to type 2 diabetes. It has recently been estimated that overweight adolescents have a 70% chance of becoming overweight or obese adults. The probability increases to about 80% if at least one parent is overweight or obese. The most immediate consequence of being overweight as perceived by children themselves is social discrimination.
There are possible adverse health consequences of being overweight or obese as such individuals are at increased risk for ailments such as hypertension, dyslipidemia, type 2 (non-insulin dependent) diabetes, insulin resistance, glucose intolerance, hyperinsulinemia, coronary heart disease, angina pectoris, congestive heart failure, stroke, gallstones, cholescystitis, cholelithiasis, gout, osteoarthritis, obstructive sleep apnea and respiratory problems, gall bladder disease, certain forms of cancer (e.g., endometrial, breast, prostate, and colon) and psychological disorders (such as depression, eating disorders, distorted body image and low self esteem) (CDC website, supra). The negative health consequences of obesity make it the second leading cause of preventable death in the United States and impart a significant economic and psychosocial effect on society. See, McGinnis M, Foege W H., “Actual Causes of Death in the United States,” JAMA, 270, 2207-12 (1993).
Obesity is now recognized as a chronic disease that requires treatment to reduce its associated health risks. Although weight loss is an important treatment outcome, one of the main goals of obesity management is to improve cardiovascular and metabolic values to reduce obesity-related morbidity and mortality. It has been shown that 5-10% loss of body weight can substantially improve metabolic values, such as blood glucose, blood pressure, and lipid concentrations. Hence, it is believed that a 5-10% intentional reduction in body weight may reduce morbidity and mortality.
Currently available prescription drugs for managing obesity generally reduce weight by primarily inducing satiety or decreasing dietary fat absorption. Satiety is achieved by increasing synaptic levels of norepinephdne, serotonin, or both. For example, stimulation of serotonin receptor subtypes 1B, 1D, and 2C and 1- and 2-adrenergic receptors decreases food intake by regulating satiety. See, Bray G A, “The New Era of Drug Treatment. Pharmacologic Treatment of Obesity: Symposium Overview,” Obes Res., 3(suppl 4), 415s-7s (1995). Adrenergic agents (e.g., diethylpropion, benzphetamine, phendimetrazine, mazindol, and phentermine) act by modulating central norepinephrine and dopamine receptors through the promotion of catecholamine release. Older adrenergic weight-loss drugs (e.g., amphetamine, methamphetamine, and phenmetrazine), which strongly engage in dopamine pathways, are no longer recommended because of the risk of their abuse. Fenfluramine and dexfenfluramine, both serotonergic agents used to regulate appetite, are no longer available for use.
Microsomal triglyceride transfer protein catalyzes the transport of triglyceride, cholesteryl ester, and phospholipids and has been implicated as a putative mediator in the assembly of Apo B-containing lipoproteins, which are biomolecules that contribute to the formation of atherosclerotic lesions. Specifically, the subcellular (lumen of the microsomal fraction) and tissue (liver and intestine) distribution of MTP have led to speculation that it plays a role in the assembly of plasma lipoproteins, as these are the sites of plasma lipoprotein assembly. The ability of MTP to catalyze the transport of triglyceride between membranes is consistent with this speculation, and suggests that MTP may catalyze the transport of triglyceride from its site of synthesis in the endoplasmic reticulum membrane to nascent lipoprotein particles within the lumen of the endoplasmic reticulum.
It has been reported that MTP/Apo B secretion inhibitors are useful in reducing food intake in mammals (European patent application publication No. 1 099 438 A2). The use of certain MTP/Apo B secretion inhibitors in the treatment of atherosclerosis and associated diseases including obesity is disclosed in a number of patents. See, for example, U.S. Pat. Nos. 5,919,795; 6,369,075 and 6,121,282.
Compounds which inhibit MTP and/or otherwise inhibit Apo B secretion are accordingly useful in the treatment of atherosclerosis and conditions frequently associated therewith. Such conditions include, for example, hypercholesterolemia, hypertriglyceridemia, pancreatitis, and obesity; and hypercholesterolemia, hypertriglyceridemia, and hyperlipidemia associated with pancreatitis, obesity, and diabetes. For a detailed discussion, see for example, Wetterau et al., Science, 258, 999-1001, (1992), Wetterau et al., Biochem. Biophys. Acta., 875, 610-617 (1986), European patent application/publication Nos. 0 584 446 B1 and 0 643 057 A1, the latter of which refers to certain compounds which have utility as inhibitors of MTP. Other examples of MTP and/or Apo B secretion inhibitors may be found in e.g., U.S. Pat. Nos. 5,712,279; 5,968,950; 6,066,653 and 6,492,365; PCT patent application publication Nos. WO 96/40640, WO 97/43257, WO 98/27979, WO 00/05201, WO 02/28835 and WO 03/002533; and European patent application publication No. 1 099 701 A1.
Although investigations are ongoing, there still exists a need for a more effective and safe therapeutic treatment for reducing or preventing weight-gain.